The present invention relates generally to interface devices between humans and computers, and more particularly to computer interface devices that provide force feedback to the user.
Computer systems are used extensively in many different industries to implement computer controlled simulations, games, and other application programs. More particularly, these types of games and simulations are very popular with the mass market of home consumers. A computer system typically displays a visual environment to a user on a display screen or other visual output device. Users can interact with the displayed environment to play a game, experience a simulation or "virtual reality" environment, or otherwise influence events or images depicted on the screen. Such user interaction can be implemented through the use of a human-computer interface device, such as a joystick, "joypad" button controller, mouse, trackball, stylus and tablet, foot or hand pedals, or the like, that is connected to the computer system controlling the displayed environment. The computer updates the game or simulation in response to the user's manipulation of a moved object such as a joystick handle or mouse, and provides feedback to the user utilizing the display screen and, typically, audio speakers.
In some interface devices, haptic (e.g., tactile) feedback is also provided to the user, more generally known as "force feedback." These types of interface devices can provide physical sensations to the user manipulating the physical object of the interface device. Typically, motors or other actuators are coupled to the interface object and are connected to the controlling computer system. The computer system receives sensor signals from the interface device and sends appropriate force feedback control signals to the actuators of the interface device in conjunction with simulation/game events. The actuators then provide forces on the interface object. The computer system can thus convey physical sensations to the user in conjunction with other visual and auditory feedback as the user is grasping or contacting the object of the interface device. Force feedback interface devices can provide a whole new modality for human-computer interaction.
Force feedback input/output (I/O) devices of the prior art have concentrated on providing maximum haptic fidelity, i.e., the realism of the haptic feedback was desired to be optimized. This is because most of the force feedback devices have been targeted at the specific needs of highly industrial or scientific applications, and not a mass consumer market. To attain such realism, design concerns useful the mass market such as low size and weight, low complexity, programming compatibility, low cost, and safety have been sacrificed in the prior art. As a result, typical force feedback interface devices include complex robotic mechanisms which require precise, bulky, and expensive components that have significant power requirements and are difficult to program for applications.
In addition, the prior art force feedback devices typically use a host computer to close a control loop around the system to generate sensations and maintain safety and stability through direct host control. FIG. 1 illustrates a block diagram of a control system 2 having a typical host controlled loop. A user manipulated object 3, such as a joystick or similar object, is moved by a user to interface with a host computer 4 with a display device 5. Sensors 6 detect the position of the user object in provided degrees of freedom and may also include buttons or other controls that detect user actions such as the press of a button. The sensor data including positional and button data is sent to host computer 4 over a bi-directional communication bus 7 that is typically connected to an interface card plugged into the host computer. To complete the control loop, host computer 4 sends force commands over bus 7 to actuators 8, and the actuators output forces on the object 3 to the user. The functions of reading sensor data and outputting force values to actuators 7 can be a burden on the host processor which detracts from the performance of the host in other host tasks and application execution.
An important concern for a force feedback interface device is communication bandwidth between the controlling computer and the interface device. To provide realistic force feedback, the complex devices of the prior art typically use high speed communication electronics that allow the controlling computer to quickly send and update force feedback signals to the interface device. The more quickly the controlling computer can send and receive signals to and from the interface device, the more accurately and realistically the desired forces can be applied on the interface object. In addition, using a high bandwidth communication interface, force feedback can be accurately coordinated with other supplied feedback, such as images on the video screen, and with user inputs such as movement of the object, activated buttons, etc.
A problem is evident when prior art force feedback interface devices are provided to the mass consumer market. Most home computers have a built-in standard serial communication interfaces, such as an RS-232 interface, RS-422 interface, "game port", Universal Serial Bus interface, or Ethernet interface that may conveniently be used to connect peripherals like a force feedback interface device to the host computer. In addition, manufacturers prefer to provide peripheral devices that use these serial interfaces, since no additional hardware, such as interface cards, needs to be provided with such peripherals. The manufacturing cost of the peripheral device can thus be significantly reduced. However, these standard serial communication interfaces are typically quite slow (i.e. have low bandwidth) compared to other communication interfaces. Realistic and accurate force feedback thus becomes difficult to provide by a controlling computer system to a prior art interface device connected through such a serial interface in comparison with other interfaces such as a direct interface card (e.g., ISA or PCI card) connecting to the data bus of the host computer.
Another important concern in the mass market industry is the issue of user safety. Because a force feedback device can impart physical forces upon the user, the potential for injury must be carefully addressed. To provide a safety measure for the user, the force feedback devices of the prior art typically include a safety or "deadman" switch which the user must activate to allow forces to be applied to the user manipulable object. If the user does not close the switch, no forces can be output. The safety switches of the prior art are typically a button or a pedal which the user must continually press or hold down to allow power to be received by the actuators. However, such safety switches can be cumbersome and/or tiring for the user to close, since the user must constantly maintain a particular grip or position to feel forces. In addition, these types of safety switches are easy to defeat by users; for example, an elastic band can be wrapped around a safety button to keep the button depressed, which defeats the entire safety purpose of the safety switch.
Finally, mass market force feedback interface devices must necessarily be low cost devices that are simple to manufacture so that the device is competitively priced in the high volume, aggressive home computer and home video game markets.